Process of hardening alloys by indiffusion of a metalloid



Patented Jan. 10, 1950 PROCESS or HARDENING ALLOYS BY [IN DIFFUSION F A .lVIETALLOID Mari Johan Drnyvesteyn' and Jan Laurens Meyerr ing, Eindhoven, Netherlands, assigno'rs toHartford National Bank and TrustCompany, Hartford, C0nn., as trustee p No Drawing. Application May'3,'1946, Serial No.

667,120. InBelgium February 8, 1945 Section 1, Public Law 690, August 8. 194

Patent expires February '8, 1965 It is known to harden a metal and more particularly an iron alloy by making diffuse into t at increased temperature a metalloid such as nitro- 4 Claims. (01.1148-132) gen, for example by heating in an atmosphere,

or a molten mass containing ;a compound of nitrogen. Reaction of nitrogen diffused inthe metal with one or more constituents of the metal to be hardened has theefiect oi producinginitrides, resulting 'in' hardening; Such a nitride hardening is utilised for obtaining a 'harde'ned superficial layer-of a metal. 1 j,

The Belgian Patent Specification 454,567 'describes an alloy, more particularly-of silver, copper or nickel, which is to be hardened by making L oxygen diffuse into it at increased temperature, which leads to the production of sub-microscopic oxides in the'allo-y, whichbrin'g "about the hardening effect. This so-called oxidation hardening may serve for a superficial hardening as well as for a hardening through the whole oftheal- 10y. 'I p Q The alloys hardened 'by indiffusio'n of afmet'al: loid are frequently brittle', du'e. to which their use is in definite case's rendered impossible.

According to the invention, for reducingthe brittleness the alloy is hardened in the monocrystalline state.

The invention is particularly of importance for alloys, such as copper and silver alloys, which are hardened by indiffusion of oxygen. The brittleness is in this case suppressed so strongly that the monocrystalline alloy, after being hardened, may be readil formed into rods, supports, strips, etc. by rolling, drawing or a similar operation,

even at room temperature. It is thus possible to obtain products which are hard, ductile and have a high'ielectrical conductivity and which, for example, lend themselves very well to the manufacture of components in thermionic tubes, such as grid backbones and wires. Also with indiffusion of nitrogen, alloys of considerable less brittleness are obtained by utilising the invention.

If with the use of the invention the alloy, after being hardened, is not rolled or deformed in another manner, it remains in the monocrystalline state, although one cannot say that in the above-mentioned embodiment of the invention, in which the hardening process is followed by a deformation, the alloy becomes polycrystalline in the usual sense of the word.

In the latter case the monocrystalline structure is broken, however, by shearings of crystal parts relatively to one another, resulting in slide lines. The monocrystalline alloy deformed subanother..; Wlien such crystal sequent tothe hardening process has a" very particular structure'which becomes manifest in'the 'factthat the deformation does not {bring about any'further appreciable increase of hardness and that upon-annealing, thejdeformed alloy neither ecrys'tallises, nor does there occur a decrease in hardness; Wemean. here an annealing process under condition's'fin which the same deformed alloy' in" which 'omyn'o- 'metalloid is indifiused. does recrystallise. For the practical use it is, of the utmost importance that the hardness is retain'edafter anneaung'. 1 f

"During the annealing'the alloy doesnot reach the very softst'atefwhich 'recrystallizing alloys usually pass atfth'e timefof their recrystallizatio'ri and-which, wh'e'n 'deformed alloys arebeing annealed, causevariations of shape if these at loys'are exposed to anystress during the an nealing process. 1

The improvement inbrittl'eness' obtainedfby the invention is probably connected with the fact that the nitrides and oxides which are formed during the hardening process also separate out at -the surfaces-where the crystals adjoin one x boundaries aref no't present in. the a11cy-;-iri the case of am'Onocry'staI for instance, brittleness is considerably -smaller. Small inclusions and pores in a monocrystal are, of course, not detrimental to the hardness and the expression monocrystalline state, consequently comprises monocrystals having such inclusions and pores.

In manufacturing an object or constructional part according to the invention it will sometimes not be necessary that the whole of the object or constructional part has minimum brittleness. In such a case it suffices if the portion of the object which is exposed to a mechanic load and whose brittleness should be decreased is in the monocrystalline state during the hardening process.

Examples crystal was rolled cold into a plate of 0.5 mm.

thick, during which treatment the hardness raised to 146 kgs./mm. This plate was entirely free from cracks. After annealing in nitrogen for half an hour the hardness was 122 kgs./mm.

Example I was completely hardened by heating" it in air for 26 hours at 950 C.. After remoyal of the oxide film, the diameter of the mODOCIYStSJf" was 1.6 mms. The Vickers hardness was 120 kgs/mmf rolled cold into a plate of 0.5mm.fithicld' 'during which treatment the hardness. remainedunvaried. Annealing for half an hour at 800 C. in nitrogen did not vary thehardness ands'anyre crystallisation did not occur duringthis process.

When the monocrystal was annealed in air for 17.5 hours only, a core of about 0.5 indiameter remained unhardened. This'core did recrystallise during annealing in nitrqgen:.. .The.

'1. The method of manufacturing=;a;hardened body comprising. :the steps 1ofrheating a: monocrystalline alloy body tqan elevated temperature,

diffusing .a metalloid selected from the group conting-oi oxygen and nitrogen-into said'alloy body :while the said alloy body is;maintained at the-said elevated temperature, andthereafter deforming the said alloy body. .2. The method of manufacturing a hardened body, comprising th stepsofheating asmono ory'stallinesilyermagnesium; alloy-body to 'a tern-.- iperature of about 800--C., diffusing oxygen into said alloy body while the said alloybody is.-:maintained at the said temperature,;cooling the csotreated, alloy body, and thereafter deforming the eidb dm-- 3. The method of manufacturing a hardened body, comprising the steps of heating a mono- -.-crys talline copper-beryllium alloy body to a tem- "perature of about 9509 .C.,-diffusing oxygen into said alloy body while the said alloy body is main- "..tained at the said temperature, cooling the sotreated alloy body, and thereafter deforming the said. alloy body. "*4JjThe method 'of manufacturing a hardened .9 body having hardened surface portions, comprisingthesteps of heating a monocrystalline copperberylliumalloy' body to a temperature of about 950- 0., diflusing oxygen into said alloy body whilel the alloy body is maintained at the said 151,1temperaturegdeforming the so-treated alloy body,

and annealing the deformed alloy body at a temperature .of '1 about 800 C. in a nitrogen atmosphere.

p MARI JOI-IAN DRUYVESTEYN.

JAN LAURENS MEYERING.

y ici The following references fi emf this -patent:-- v

-. ews-ems ei N are of record in the L ;....Name j .Date 4,431,554 7 Fry .Mar. 18, 1924 i eo ssiliufyan.Arke1. Oct. 5, 1926 80 2 ,012,325 ..Milner'\ Aug. 27, 1935 7 2,145,690 Hansel 7 Jan. :31, 1939 2 3oo-,27a;- .,nah1-i e a .oct. 27, 1942 Fear-f w PA E T 35 Number. .Country J Date 315.4356? 1 r Feb. 26, 194:4

. ""QTHERYB'EFERENCES ol. NO- 9, March 1930 may? i 

1. THE METHOD OF MANUFACTURING A HARDENED BODY, COMPRISING THE STEPS OF HEATING A MONOCRYSTALLINE ALLOY BODY TO AN ELEVATED TEMPERATURE, DIFFUSING A METALLOID SELECTED FROM THE GROUP CONSISTING OF OXYGEN AND NITROGEN INTO SAID ALLOY BODY WHILE THE SAID ALLOY BODY IS MAINTAINED AT THE SAID ELEVATED TEMPERATURE, AND THEREAFTER DEFORMING THE SAID ALLOY BODY. 